1. Technical Field
The present invention relates to a process of deriving data on objects.
2. Related Art
In general, a radar device receives reflected waves from objects, and derives moving targets or still targets on the basis of the peak signals of the reflected waves. The radar device outputs target data on those targets to a data using device which uses the target data. The data using device is, for example, a vehicle control device which controls a vehicle. The vehicle control device controls behavior of the vehicle by using the target data acquired from the radar device, thereby providing safe and comfortable running to a user of the vehicle.
Also, if the radar device derives a still target existing in the running direction of the vehicle, it determines whether the still target is a roadblock to obstruct the progress of the vehicle. In a case where the still target is a roadblock such as a stopped vehicle, there is a possibility that the vehicle will collide with the roadblock. For this reason, in a case where the possibility that the still target is a roadblock is high, the radar device outputs target data on the still target to the vehicle control device. If acquiring the target data, the vehicle control device performs vehicle control such as deceleration on the vehicle, thereby avoiding collision of the vehicle with the roadblock.
In contrast, in a case where the possibility that the still target is a roadblock is low, the radar device does not output target data on the still target to the vehicle control device. Examples of still targets other than roadblocks from which the radar device derives include upper objects such as road signs and traffic lights installed over roadways, and roadblocks such as guardrails provided at the sides of roadways. Still targets such as upper objects do not have a risk of colliding with vehicles. Therefore, in a case where the possibility that a derived still target is not a roadblock is high, the radar device does not output target data on the corresponding still target to the vehicle control device.
Here, in order to determine whether each of derived still targets is a roadblock, for example, the radar device includes a first transmitting antenna which outputs a transmission wave upward with respect to the surfaces of roadways, and a second transmitting antenna which outputs a transmission wave downward with respect to the surfaces of roadways.
In this case, if transmission waves output from the first transmitting antenna and the second transmitting antenna are reflected from a still target, the radar device determines whether each still target is a roadblock, on the basis of the signal level difference between the reflected waves, the temporal transitions of the signal levels of the reflected waves, and the like. Also, as a technology related to the present invention, for example, there is Patent Literature (JP-A-2011-221869).